1. Field of the Invention
The present invention relates to an obstacle monitoring (or detecting) device for vehicles, especially for helping to ascertain safety in a direction rearward from the vehicle.
2. Description of the Prior Art
A prior art device will be described with reference to FIG. 1, which is one of the drawings indicated in the brief description of the drawings. A prior art device comprises a plurality of obstacle detector 1a, 1b, 1c which scan the rearward direction with ultrasonic waves or light, detect obstacles in the monitoring domain and output pulse signals, and a monitor 2 which informs the driver of the existence of the detected obstacle based on the pulse signals, as shown in FIG. 1. The obstacle detectors 1a, 1b, 1c are mounted outside of the vehicle at its back portion, while the monitor is mounted in a compartment of the automotive vehicle.
Devices having a conventional constitution, as shown in FIG. 1, however, require a trigger signal line 3 for transmitting a trigger signal from the monitor 2 to each obstacle detector 1a, 1b, 1c; detection pulse signal lines 4a, 4b, 4c for transmitting detection pulse signals from each obstacle detector 1a, 1b, 1c to the monitor 2; and power supply lines 5, 6. The result is a large number of wires in the wire-harness between the obstacle detectors and the monitor. This further results in complicated connection for the wiring work between the obstacle detectors outside the vehicle and the monitor inside the vehicle.
The present invention is proposed in order to eliminate the above-mentioned disadvantages.